I want to cancel the QR reader that was purchased

To cancel a subscription, go to:

Settings → Apple ID → Subscriptions

Select the subscription you would like to cancel, tap in and select "Cancel Subscription" If you are in the middle of a period, you will have access to subscriptions until it expires. After that, the subscription closes permanently.

You can find more useful information here:

If you want to cancel a subscription from Apple - Apple Support

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For Refund:

If you see 'apple.com/bill' on your billing statement - Apple Support (CA)

To cancel a subscription, go to:

Settings → Apple ID → Subscriptions

Select the subscription you would like to cancel, tap in and select "Cancel Subscription" If you are in the middle of a period, you will have access to subscriptions until it expires. After that, the subscription closes permanently.

You can find more useful information here:

If you want to cancel a subscription from Apple - Apple Support